Telephone-exchange system



E H. CLARK.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEC. 11, 1919.

1,426, )1 7, Patented Aug. 22, 1922.

//7 ve/vfor:

EDGAR GLA.RK, 01F R-IOHIVIOND HILL, NEW YORK, ASSIG'NOR TO WESTERN ELEG- TRIO CDMPANY, ENGORPORAQED, 035 NEW YORK,

YORK.

N. Y., A CORPORATION OF NEW TELEPHONE-EXCHANGE S'EZ'Ea'TET/i.

Specification of Letters Patent.

Patented Aug. 22, 1922.

Application filed December 11, 1919. Serial No. 344,095.

To all whom it may concern Be it known that l, EDGAR H. CLARK, a citizen of the United States, residing at Richmond Hill, in the county of Queens, State or New York, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a tall, clear, concise, and exact description.

This invention relates to telephone eX- change systems of the semi-automatic type, and more particularly to the type employing a B operator for extending a connection semi-automatically from an originating operators position to a terminating operators position over a two conductor trunk.

The object of the invention is the provision of means permanently bridged the two conductors oi? an intero'lfice trunk for holding the trunk busy at its outgoing end until after the trunk is released at its incoming end.

A further object of the invention is the provision of means under the control of the terminating operator and operable over the two conductors of an interorlice trunk terminating in such operators position for making such trunk busy at will to calls outgoing from the originating o'llice.

The main feature of the invention resides in the provision of high resi tance relay permanently bridged across the two conductors of the trunk circuit extending between two ofiices, which because of its high resistance does not energize during the building up and continuance of a connection over the trunk circuit and does not therefore interfere with the normal functioning of the system, but which energizes upon release of the trunk circuit at the outgoing end to place a busy potential upon the test terminal of the trunk appearing in the banks of all oil-lee switches at the originating oilice having access thereto. This busy condition is maintained until the terminating operator pulls down the connection at her position. lVhile the primary function of this holding relay is as above described to hold the interothce trunk busy until the terminating operator pulls down the connection, the relay may also be employed to place an artificial busy condition on the outgoing terminals of the trunk at the will of the terminating operator.

These and other features of the invention will become more apparent as the description progresses. Reference will now be made to the accompanying drawing which shows only so much of the circuit and apparatus associated with the posit-ions of an originating operator 0, a B operator 0, and a terminating operator G as is neces sary for an understanding of the invention, together with a subscribers line C terminating before the position 0 of the terminating operator.

The circuits of this system are designed to be employed in connection with the corresponding circuits disclosed in the co-pending application of rilben E. Lundell and Edgar H. Clark Serial No. 199,886, filed November 2, 1917, Patent 1,842,823, June 8, 1920. inasmuch as the invention involves only portion of the apparatus of the B operators position and terminating operators position, it is not deemed necessary to an understanding of the invention to show the entire circuits necessary for extending a connection from the line of a calling subscriber to and through the circuits at the terminating operators position to the line of the desired subscriber, and therefore only so much of the circuits as are required to tally disclose the novel features of this invention have been disclosed.

The manner in which they circuits are organized will best be presented in connection with a description of the mode of their operation. It will be assumed that an originating operator at position 0 has seized the trunk line shown in the drawing terminating in the B operators position 0, and that in response to the instructions of the originating operator the B operator has set the impulse controlling registers of her position for selecting a trunk outgoing from such position and terminating in a plug ended cord circuit at an outlying oflice in which the line oi the desired. oflice terminates, and for setting the number indicating register at the terminating oilice to register the designation of the. desired line be- LfOlG the terminating operator by means of apparatus shown more in detail in said application hereinbefore referred to.

The association of the calling plug (not shown) of the originating operators cord circuit with the trunk jack J, has, in the well known manner, caused the energization of sleeve relay 2 which at its armature and -7 of the otfice selector,

front contact connects the polarized supervisory relay 3 across the trunk conductors 1 and5 extending to the position Oto the B operator. In response to the seizure or the trunk circuit 1-, 5, the registers of the register sender at her position in accordance with the designation of the desired line which is communicated to her by the originating operator, which register sender then proceeds in the well kIlOWn manner to set the brushes 6, 7 and 8 ot the otiice selector upon the terminals of an idle 'trunkcircuit leading to the oiiice in which the desired line is located.- Following the setting of the oflice selector, the sequence switch associated with the office selector moves its cam springs 9 and 10 into position 11 in which position the impulse sender at the B operators position is associated with the conductors 1.1 and 12 of the interotlice trunk in readiess for the transmission of impulses over the trunk for setting the call indicator at the terminatingoperators position 0 Upon the establishment of the circuit over the interotfice trunk, relays 13 and 1 1 become energized. The circuit of these relays may be traced from grounded battery through the right-hand winding of relay ltat the B operators position, through'the lower contact of sequence switch spring 15 (14) of the sender sequence switch of the B operators position, through the lower contact of 10 (11), over brush trunk conductor 12, the lower armature and back contact of relay 16, the inner normally closed armature contacts or reversing relay 17, the left-hand winding of relay 13,..the outer left-hand armature and back contact of relay 18, the back contact and inner left-hand armature ofrelay 18, the right-hand winding of relay 13, the outer normally closed armature contacts of reversing relay 17, the upper armature and back contact of relay 16, trunk conductor 11, brush 6 of the otlice selector, lower contact of sequence switch spring 9 (11), the lower contact of the sender sequence switch spring 19 (14), and thence to ground through the left-hand winding of r lay 14. Relay 13 energizes in this circuit and establishes a circuit for the slow acting relay 20, which may be traced from grounded battery through the winding of this relay and sequence switch spring thence to groundthrough front contact and Relay letthand armature or relay 13. 20 upon. energizing establishes at its armature and front contact, a locking circuit for itself extending through its winding and -through the back contact and armature of sleeve relay 21 and thence to ground through the left-hand winding of relay 18. Relay 18 does not energize at this time however, since its winding is short-circuited atthe left-hand armature and front contact ot'relay 13. At

B operator sets the through the contact of sequence switch spring 23.

Sequence switch 22 upon leaving. position 1 1- disconnects relay 1% from the trunk circuit -and connects the relay 2 1 to the trunk circuit, through the upper contacts of sequenceswitch springs 15 and 19. Since now battery potential at the windings of relay 14 has been disconnected from the trunk, the energizing circuit of relay 13 at the termin ating otlice is destroyed and relay 13 thereupon deenergizes, opening at its left-hand armature and front contact the shunt circuit which has prevented the'energization of relay 18. Relay 18 thereupon energizes closing at its right-hand armature and front contact a locking circuit extending through its right-hand winding and to ground over the conductor 25 which extends to the holding circuit ofthe terminating operators call indicator as fully disclosed in the application hereinbetorereterred to. At its lefthandarmatu'res and back contacts relay 18 disconnects the metallic loop which was normally connected across the windings of relay 13 andat these armatures and front contacts 1 connects grounded battery and ground re spectively to the right-hand and left-hand windings of relay 13. Relay 13 re-energizes and at its armature and front contact establishes a circuit for the relay 26 which circuit may be traced from grounded battery through the winding of this relay and thence to ground. at the front contact and left-hand armature of relay 13.

The energization of relay 26 establishes a circuit for the assignment lamp 27, which circuit may be traced from grounded battery through the assignment lamp, through the outer right-hand armature and back contact 01 the assignment relay 414;, through the inner left-hand armature and baclr contact of relay 28and thence to ground through the front contact and armature of relay 26. The terminating operator upon noting the illumination of the assignment lamp 2'? depresses the assignment key K indivdual to the trunk circuit which has been taken for use, thereby closing a circuit for the assignment relay 1 1 and for the holding relay of the call indicator (not shown) associated with her position, which circuit may be traced from ground through the contacts of the assignment key K, the right-hand winding of relay 1 1, the back contact and outer left-hand armature of relay 28, thence over the conductor 29, through the holding relay of the call indicator and to grounded battery. Relay energizes in this circuit and at its eithand armature and trout contact establishes a holding circuit for itself inde pendent of the contacts of the assignment key, which circuit be traced from ground through the left-hand armature and front contact, thence through both windings of relay 4% and to grounded battery over the circuit previously traced. At its outer right hand armature and back contact, assignment relay 14i opens the circuit of the assignment lamp 27 causing this lamp to become extinguished and at its inner right-hand arniature and front contact closes circuit for the relay 16 which may be traced froin grounded battery through the inner righthand armature and trout contact of relay id and thence to ground through the winding 01 relay 16.

The energization of relay l6 disconnects the interoihce trunk conductors 11 and 12 from the windings of relay l3, and connects these trunlr conductors to the impulse conductors 30 and 31 extending to the call indicator t the terminating operators position. The extension of the trunk circuit to these impulse conductors causes, in the manner set forth in the application hereinbeiore referred to, the operation of the sending mechanism at the B operators position to send impulses to the call indicator at the terininating operators position in accordance with the setting of the registers the B operators position for setting up the designation of the desired subscriber upon the call indicator at the terminating operators position.

The terminating operator upon noting the designation of the desired line upon the lamps of the call indicator takes up the plug P in which the selected trunlr circuit terminutes and, after making the usual test of the ack of the desired line to determine the busy or idle condi ion of this line, inserts the plug in the jack J. A circuit is now established through the cut-oil r lay 32 of the called line over the sleeve terminals of the plug and jack through the winding oi the sleeve relay 2i and thence to grounded battery through the winding of relay 28.

The energization of sleeve relay 21 discon nects at its upper armature and back contact the connection between the tip oi the plug and the test conductor leading to the opera tors headset, and at its rniature and front contact extends a connection from the tip of the plug to the upper right-hand winding of the repeating coil 33. At its lower armature and back contact, sleeve relay 21 opens the initial energizing circuit of relay l8 and closes a. new energizing circuit for relay 18 extending from grounded battery through the front contact and lower armature of res econnects the relay 1.3 to these runlr conductors. Relay 13 which deeneraed at the time relay 16 was energized now re uergizes relay 26 and maintains this re l energized until the release of the interonice trunlr circuit at the originating oiiice. Ail; its inner left-hand armature and baclr contact, relay 28 further opens the circuit of the ase'gnnient lamp 2'? for preventing further illumination of this lamp.

At its right-hand armature and front contact, relay 28 establishes circuit for initiating the application oi ringing current to the line of the desired subscriber. This circuit may be traced from grounded battery through the disconnect lainp 34, through the right-hand armature and front contact of relay 28, the back contact and armature of ringing cut-off relay 35, the hack contact and left-hand armature of relay 36 and thence to grounc through the winding of ringing relay 3'7. Ringing relay 37 energizes in this circuit but the resistance of this relay is Sdl'l'lClQllt to prevent the illuinination of lamp At its arinatures and front contacts, relay 8'? connects a source of ringing current to the line of the called subscriber, the circuit over which the ringing current flows extending from the source of ringing current, through the winding oi the ringing cut-oil relay 35,- through the front contact and lower armature or ringing relay 8?, over the ring contacts of the plug and jack, over one limb of the called subscribers line, through the ringer 38 and condenser 39 at the substation of the called subscribers line, thence baclr Yer the other limb or" the subscribers line, through the tip contacts of the jaclr and plug, the front contact and uooer armature of sleeve relay .L U

and thence to ground through the upper armature and front contact oi ringing relay 37.

The called subscriber upon responding to the call removes his receiver from its switchhoolr thereby reducing the resistance of the circuit just traced, causing the energization of the ringing cut-oil? relay 8-5 in the well known manner. The enei izatio-n oi this relay opens at its armature and back contact the shunt which heretofore extended around the winding of relay 36. Relay 3?) now energizes in series with the ringing relay 37 and at its left-hand armature and front contact establishes a locking circuit for itselt extending from its winding to grounded battery through the front contact and righthandarmature of: relay 28. The connection of this locking ground. to the winding of relay 86 places a shunt around of the ringing relay 3''? thereby causing the deenergization of relay 37. The deenergization of relay 37 disconnects at its armatures and front contacts the source of ringing current and ground from the tip and ring contacts of the plug, and at its armatures and back contacts connects the tip and ring contacts of the plug to the right-hand windings of the repeating coil 38. he calling sneervisory relay 10 now energizes in a circuit extending over the called suhscribefis line, which may .be traced from grounded battery through the lower ripdrt-hand winding of the repeating coil 33, the winding of the calling supervisory relay 110, and lower armature of relay 37, the ring contacts ofthe plug and jack, over the subscribers lineloop, over the tip contacts oi the plug and jack, the :h'ontcontact and upper armature oi? sleeve relay 21, the upper armature and baclr contact oi relay and thence to ground through the upper right-hand winding of repeating coil The energization oil? supclyisory relay and relay 36 establishes afcircuit tor "the versing relay 17 which may be traced tron:

grounded battery through the winding of relay 17, armature and front contact of supervisory relay 10 and thence to ground through the right-hand armature and front contact of relay 36.

The energization of reversing relay 1? causes the reversal of the battery leads ere tending through the windings of relay and thereby causes a reversal in the direction of the current flowing over the interoflice trunk and through the windings polarized supervisory relay 3 at the Oll. hating operators position. This supervisory circuit may be traced. from, grounded battery through the front contact and innor left-hand armature 0t relay 18, the right-hand winding of relay 123, the make contacts of the outer ri; it-hand armature of relay 17, the lower le'lit-hand winding. of repeating coil. 83, the back contact and lower armature'ot' relay 16, the trunk conductor 12, brush 7 of the oiiice selector, the upper contact of sequence switch spring 10 (1.2), the sequence switch of the olhce selector having moved into position 12 following the setting of the cal] indicator at the terminating operators position, trunk conductor through the lower right-hand winding of repeating coil ll, the armature and front contact oi sleeve relay 2, the windings o the polarized supervisory relay 3, the upper right-hand Winding of repeating coil 41,

the winding back Contact l of the I trunk conductor a, the upper contact of sequenceswitch spring 9 (12), the brush 6 of the oi'lice selector, trunk conductor 11, the upperv armature and back contact of relay 16, the upper left-hand winding of repeating coil 33, the make-contacts of the inner armature of relay 17, the left-hand winding oi? relay 13, and thence to ground through the outer left-hand armature and front contact of relay 18. The polarized supervisory relay 3 energizes in such a manner to signal the originating operator that the called subscriber at the terminat ing operators position has responded to the call. During the establishment. of the connection, "the high resistance relay 42 has been bridged across the conductors 11 and 12 of the interoli'ice trunk circuit at the outgoing end or the trunk circuit, but due to its high resi ance and to the comparatively low resistance of the windings of relays 13, 14 and 3, relay has not diverted suflicient current through its own winding to interfere with the proper functioning of the other relays above mentioned which have been connected across the trunk circuit at various stages in the establishment of the connection, and the relay 12 has not received SUIllClQIlhCllllGllt to cause its own energization. Upon the termination of the conversation, and the restoration of the receiver to its switchhook' at substation C oi? the called line, the calling supervisory relay 10 becomes deenergized and thereby opens the circuit 01511116 revers- 1.00 lug relay 17, which in turn deenergizes and again reverses the connection of the battery lo s to the conductors 11 and 12 of the ii., ero.tlice trunk; circuit. The reversal in the direction of current flow over the trunk circuit'causes the polarized supervisory relay 3 at the originating ofiice to be energized in such a manner as to give the originating pcrator an indication that the called subscriber at the terminating oilice has released.

The originating operator thereupon removes the calling alug o1 her cord circuit from the jack J thereby opening the circuit of sleeve relay The circuit previously traced extending through the windings of the polar- 11 ized relay and the windings of relay 13 at the terminating oliice, is now opened at the armature contacts of sleeve relay 2, and relay 13 is thereby deenergized, opening at its armature andtront contact the circuit of relay 26.v Relay 26 thereupon deenergizes, closing at its armature and back contact a circuit for the disconnect lamp 34s. The circuit of lamp 3 1; may be traced from grounded. battery through this lamp, the *"ght-hand armature and front contact of relay 2.8 and thence to ground at the back contact and armature or relay 26.

Upon the opening of. the trunk circuit at the contacts ofsleeve relay 2, the low resistance bridge extending across the in otlice tiunlr through the windings of s visory relay 3 is removed from around winding of the high resistance relay 12, this relay thereupon receives suihcient current through the windings oi"- relay 13 to cause its eiiergization. delay 13 however, does not remain energized in series with relay 42. Relay 4:52 at its armature and tr nt contact connects ground to the multiple test terminals 43 appearing in the banks 01"- all ofiice selectors which have access to the trunk 11, 12 for the purpose of n alring this trunk circuit busy until the terminati operator has released the trunk the terminating oflice. At the time the originating operator pulled. down the connection with the interoliice trunk at her position, the apparatus at the originating otiice and E operators position which was utilized in tablishing the connection with the interoitice trunlr was restored to normal position in the well known manner.

The terminating operator upon noting the illumination of the disconnect lamp 34; removes the plug 1 from the eel: 5 cansing thereby the deenergization of: sleeve relay 21 and of relay 2S, VThe deene tion of relay 28 opens the circuit of the disconnect lamp 34:, and at its left-hand armatures and back contacts restores the circuits of the assignment relay 4 1 and the assignment lamp 27. The deenergization of sleeve relay 21 opens the locking circuit of relay 18 which thereupon deenergizes opening at its left-hand armatures and front contacts the circuit which extends through the winding of the high resistance relay 1-2. This relay thereupon deenergizes removing the busy potential from the multiple terminals 43 and freeing the interoflice trunk for further use.

Should the terminating operator at any time desire to make any or the interofiice trunks, terminating in her position, artificially busy, it is only necessary for her to insert the terminating plugs of such trunk circuits in malre-busy-jacks. Assuming that the operator desires to make the trunl shown in the drawing artificially busy, she inserts the plug P in make-busy-contact similar to the jack J, thereby causing the energization of sleeve relay 21 in the manner hereinloetore set forth. This relay at its lower armature and front contact establishes a circuit through the left-hand winding of relay 18 which in turn at its left-hand armatures and front contacts, connects grounded battery and ground through the windings of relay 13 to the trunk conductors 11 and 12. The high resistance relay 42 energizes in this circuit, and at its armature and front contact places a busy ground potential upon the multiple terminals of the trunk to prevent seizure of this It is apparent from the foregoing de i ition that the employment of high rel ed across the conductors interotliz'ze trunk is pargoons since the trunk may without the employment of conductors and without in- .e or 1 nal ca ole in any way with the normal l the system.

- s claimed is: v V a telephone exchange system, an

or b nat oftico, a terminating oliice, a two conductor trunk circuit extending between tance relay permasaid olives, a high r 7 1 circuit at the outnently bridged LL s end thereof, neans under the control of sail. relav for placing a busy potential upon the on omg terminals of said circuit,

a d means LllQ terminating office for causthe operation of said relay, 2. In a tele tihone excha e system, an 7 all othce, a two conductor trunk circuit extending between said oliices, a high resistance relay permanently bridged across said circuit at the outgoing end thereof, means under the control of rid rela loi 'ilacing a l :y potential upon the outgoing terminals of said circuit,

orig natin otu and means at the terminating oliioe :i'or causmg the operation of said relay upon discon om the terminals said trunk cirt the originating 011108.

0. in a telephone exchange system, an originating otlice, a terminating oflice, a two conductor trunk circuit extending between said othces, a high resistance relay permancntly bridged across said circuit at the outgoing enc thereof, moans under the control of said relay for placing a busy potential upon the outgoing terminals of said circuit, and means at the terminating ofiice for calls the operation of said relay upon disconnection from the terminals of said trunk circuit t the originating oilice, and for maintaining the energization of said relay until the release of the circuit at the terminating otlice.

l. In a telephone exchange system, an originating oliice, a terminating office, a two conductor trunk circuit extending between said ofices and terminating at the latter oliice in a connection plug, a high resistance relay permanently bridged across said circuit at the outgoing end thereof, means under the control of said r lay for placing a busy potential upon the outgoing terminals of said circuit, and means at the terminating orfice under the control of said connection plug for causing the operation of said relay upon disconnection from the terminals 01" said trunk circuit at the originating ofiice.

5. In a telephone exchange system, an

originating ofiice,a terminating otfice, a two conductor trunk circuit extending between said offices, a high resistance relay permanently bridged across said circuit at the outgoing end thereof, means under the control of said relay for placing a busy potential upon the outgoing terminals of said circuit, low resistance operating bridges normally connected across said circuit for enabling an extension of a connection over said circuit, said bridges rendering said relay inoperative, and means at the terminating oiiice for causing the operation of said relay upon the disconnection of said low resistance bridges from said circuit.

6. In a telephone exchange system, an originating office, a terminating o'flice, a two conductor trunk circuit extending between said offices and terminating at the latter office in a connection plug, a high resistance relay permanently bridged across said circuit at the outgoing end thereof, means under the control of said relay for placing a busy potential upon the outgoing terminals of said circuit, low resistance operating bridges normally connected across said circuit for enabling an extension of a connection over said circuit, said bridges rendering said. relay inoperative, and means under the control of said connection plug for causing the operation of said relay upon the disconnection of said low resistance brid es from said circuit.

7.-In a telephone exchange system, an originating oflice, a terminating office, subscribers lines terminating in said latter otlice, a two conductor trunk circuit extend ing between said oliices and terminating at the latter o-flice in a connection plug, a high resistance relay permanently bridged across said circuit at the outgoing end thereof, means under the control of said relay for placing a busy potential upon the outgoing terminals of said circuit, low resistance operating bridges normally connected across said circuit for enabling the extension of a con nection over said circuit, said bridges rendering said relay inoperative, means for causing the operation of said relay upon the disconnection of said low resistance bridges from said circuit, and means fordeenergizing said relay upon removal of said plug from the jack o1 the called subscribers line.

8. In a telephone exchange system, an originating ofiice, a terminating oflice, a plurality of two conductor trunk circuits extending between said O'ifiCGS, high resistance relays permanently bridged across said circuits at the outgoing ends thereof, and means at the terminating office for causing the-operation of said relays at will to render any or all of said circuits artificially busy.

In witness whereof, I hereunto subscribe my name this 5th day of December A. 1).,

' EDGAR H. CLARK. 

